Like a 550,000-square-foot sponge, the vegetative roof assembly (VRA) atop the Douglas A. Munro Coast Guard Headquarters Building in Washington, D.C., absorbs rainfall while managing its release into the city’s sewer system. Green roofs are a storm water management “best practice” in the nation’s capital, which boasts more than 3.2 million square feet of green roof space.

Gordon Contractors installed the green roof on the 11-level, 1.2-million-square-foot headquarters, which is also home to several independent field commands including the National Pollution Fund Center and Marine Safety Center. Key performance objectives included complying with D.C.’s stringent storm water regulations, as well as federal Environmental Protection Agency (EPA) rules requiring 95 percent of storm water to be collected onsite.

Beyond complying with local and federal storm water mandates, the project team creating the vegetative roof sought to create a rooftop habitat that supports biodiversity and helps birds and other wildlife thrive. The result of a careful and collaborative approach to moisture management is a high-performing roof that ultimately received LEED Gold certification from the U.S. Green Building Council. Working as a system, the roof’s components help reduce rainwater runoff while helping to reduce pollutant loads and protect natural resources such as the nearby Chesapeake Bay.

Numerous Challenges

As every roofer knows, no two projects are alike. The location of the Douglas A. Munro Coast Guard Headquarters on hilly terrain provided plenty of natural obstacles, including nine of the eleven levels being built into a hillside. The site

Gordon Contractors installed the green roof on the 11-level headquarters. Performance objectives included complying with D.C.’s stringent storm water regulations, as well as federal EPA rules requiring 95 percent of storm water to be collected onsite. Photos: Owens Corning

features a series of stair-stepped green roof terraces that help gradually move water from higher to lower levels and eventually into a pond through elevation changes of 120 feet. According to Steve Gordon, president of Preservation & Protection Systems Inc. (PPSI), the company providing design and installation support with the Owens Corning FOAMULAR extruded polystyrene insulation and Henry 790-11 Hot Rubberized Asphalt used in the VRA, the stair-step design required a complex approach to the roof’s varied elevations. To meet this challenge a complex network of expansion joints by EMSEAL tied together multiple air barriers within the system. Another challenge was the magnitude of the project, spanning more than a half-million feet across multiple levels and 176 acres. Timing was critical, as plants and vegetation required quick delivery and transplanting into their new environment, particularly during D.C.’s sweltering summers. These living materials couldn’t simply be covered with a tarp until better conditions prevailed, but had to be quickly transported, installed and irrigated.

The Douglas A. Munro Coast Guard Headquarters serves 4,000 occupants, so comfort and energy efficiency were important concerns. From the outset of the project, the integrated roofing team was tasked with designing a vegetative roof assembly that would help decrease the building’s heating and cooling energy usage, lower long-term maintenance costs and extend the life of the roof.

A Solution to Achieve Performance Goals

The project team selected a Protected Roof Membrane Assembly (PRMA) to deliver the water management required to meet storm water mandates, as well as deliver energy efficiency through R-value performance and strength to support vegetation requirements. The PRMA places the insulation layer above the waterproofing membrane, a reversal of traditional roof systems. PPSI recommended Owens Corning FOAMULAR 404 and 604 extruded polystyrene (XPS) insulations for use in the PRMA. The water resistance and compressive strength of the XPS insulation provided the integrity needed for long-term roof performance and helped the Douglas A. Munro Coast Guard Headquarters Building ultimately achieve LEED Gold certification.

The Douglas A. Munro Coast Guard Headquarters was built on hilly terrain, and nine of the eleven levels were built into a hillside. The stair-stepped green roof terraces help gradually move water from higher to lower levels and eventually into a pond. Photos: Owens Corning

Given the sheer size of the project, it was inevitable that the roofing team would encounter several scenarios requiring strategic problem-solving throughout the installation. For example, the team adjustedthe engineered soil specification to reduce the loads within the structural tolerances for the roof structure and carefully addressed a range of pH, moisture, organic matter and nutrient levels to support the variety of plants. Not only did such careful attention deliver strength performance, it’s also achieved the objective of attracting wildlife. The terraced landscape has welcomed not only birds and butterflies, but the occasional deer wandering onto a rooftop.

Evaluating Results

Since its completion, the VRA at the Douglas A. Munro Coast Guard Headquarters has attracted widespread attention from landscaping groups, engineering firms and organizations interested in sustainability. These groups are interested not just in the building’s unique design but in its resilience and performance. Steve Gordon of PPSI says the resilience of the headquarters’ roof is reflected in its record of no leaks. “We’ve had no leaks,” Gordon says. “The reason we use hot fluid applied waterproofing on green roofs is because we want to avoid any leaks in the building. At the end of the day, the biggest liability in a roof is water.”

After successfully navigating a range of challenges and opportunities, the U.S. Coast Guard Headquarters’ VRA epitomizes the convergence of aesthetics and performance and is recognizedas one of the largest green roofs in the world.According to the Landscape Performance Foundation, the headquarters’ vegetative roof retains up to 424,000 gallons of rainwater.

In a small way, the performance reflects the integrity of a hero an Act of Congress honored when naming the headquarters, according to Captain Will Smith, Commanding Officer U.S. Coast Guard Base NCR. Captain Smith noted, “The Coast Guard’s only Medal of Honor recipient, Douglas Munro earned the award for his selfless sacrifice as a landing craft pilot at Guadalcanal while evacuating marines from a beachhead under heavy fire from enemy forces.”

Western Specialty Contractors restored the roof of the Museum of Westward Expansion located beneath the Gateway Arch in St. Louis. This shows the protection board installed prior to adding the leak detection system.

The St. Louis branch of Western Specialty Contractors recently completed a project to restore and waterproof the roof of the Museum of Westward Expansion located beneath the iconic Gateway Arch on the St. Louis Riverfront. The work is part of a multi-phase project, spearheaded by nonprofit organization CityArchRiver Foundation, to expand and renovate the underground museum, plus renovate the grounds surrounding the Arch. The Jefferson National Expansion Memorial, which includes the Gateway Arch, Museum of Westward Expansion and the surrounding park, is maintained by the National Park Service.

Opened to the public in 1976, the Museum of Westward Expansion has undergone very few changes since its grand opening. The size of a football field, the museum features rare Native American Indian artifacts and materials documenting the days of Lewis and Clark and the 19th century pioneers who shaped the history of the American West.

Work on the 100,000-square-foot museum roof project began with removing sod and sandy soil covering the top of the roof and 10-28 inches of Elastizell engineered fill using a bulldozer. Next, the existing waterproof membrane was removed from the structural concrete deck.

After two layers of modified bitumen sheet waterproofing were installed, crews apply a coat of adhesive to adhere the asphaltic protection board.

Once the deck was exposed, Western crews went to work identifying and repairing leaks in the existing museum lid that had been present for many years, as the existing waterproofing had exceeded its lifespan. Several methods were used to evaluate the condition of the structural concrete deck, which included a chain-drag sounding along with visually identifying delamination and cracks.

Western crews then installed a two-ply Laurenco modified bitumen sheet waterproofing system covered with WR Meadows PC2 protection board. An electronic leak detection system followed by a permanent leak detection grid system were installed over the protection board. Crews then installed a layer of 1-1/2 inch, 60-psi Dow extruded polystyrene with an additional layer of the protection board and a J-Drain 780 drainage mat.

The next phase of the project involved waterproofing the 42,000-square-foot horizontal lid and the 37,000-square-foot vertical walls of the museum addition. Western’s scope of work in this area included installing a two-ply modified bitumen sheet waterproofing and protection board, as well as an electronic leak detection system, along with two layers of extruded polystyrene. A layer of extruded polystyrene was also installed on the vertical walls, followed by the drainage mat on both the horizontal and vertical walls.

During portions of the project Western crews were working over occupied space, as the museum was largely operational during construction.

Additional waterproofing of the north and south museum entrances encompassed approximately 13,800 square feet, which included approximately 5,000 square feet of deck around each leg of the Arch.

The museum was largely operational during construction, and for much of the project Western crews were working over occupied space. The company sequenced the removal of existing roofing material so that they could remove, clean and install new roofing material daily to keep the museum dry during construction.

Testing was a daily requirement during the waterproofing installation. Western was required to complete a pull test for every 500 square feet and take moisture readings for every 100 square feet. Daily observation reports had to be completed during the waterproofing application, with all testing results and location tests documented along with the weather conditions. Additionally, Western crews took 50 photos daily to document the testing and work area.

Construction on the Arch grounds began in August 2013, while renovations to the museum and visitor center began in April 2015. The multi-phase project is still underway, and the improved underground Museum of Westward Expansion is expected to be finished by summer 2018.

The Dow Chemical Company announces its plans to construct a manufacturing facility to be located in Burley, Idaho. The facility will be operated by Dow Building Solution (DBS), a business unit within Dow, and produce STYROFOAM Brand Extruded Polystyrene (XPS) Insulation – a thermal insulation solution facilitating sustainability and innovation in the building and construction industry since its discovery in 1941.

Building upon its 75 years of innovation, the STYROFOAM Brand Extruded Polystyrene Insulation facility will come on-line utilizing DOW BLUEDGE Polymeric Flame Retardant Technology – an invention that is transforming the market as the industry standard flame retardant for use in polystyrene foam insulation, as it meets the demands of global energy efficiency regulations and sustainable building design.

The construction of the XPS facility exemplifies Dow’s commitment to the DBS growth strategy and strengthens its ability to deliver sustainable insulation solutions to customers, especially in Western Canada and the United States. The facility also demonstrates Dow’s pledge to provide operations performance in natural resource efficiency, environment, health, and safety, as outlined in Dow’s 2025 Sustainability goals.

“The construction of this facility will allow us to respond to market demand and deliver sustainable building solutions to our customers,” said Tim Lacey, global business director for Dow Building Solutions. “The collaboration with the city of Burley has been critical to reach this agreement and we look forward to continue collaborating together into the future.”

“Dow’s decision to build in Burley speaks about the quality of our workforce, the business- friendliness of our state and communities, and the great diversity that we are developing in Idaho’s economy,” Governor C.L. “Butch” Otter said. “It’s always great to welcome a corporate citizen to Idaho, and I’m excited about the opportunities for existing Idaho businesses to help meet the supply chain needs of this new enterprise.”

“We are thrilled to have a company such as Dow locating in Burley” said Director of Economic Development, Doug Manning. “They are a leader in business and innovation, and the immediate and future economic impact on this community will be exceptional. It’s a ‘win’ for the City of Burley to have a Fortune 50 Company locating here. This has been a collaborative effort from the State, the City, Burley Development Authority, Southern Idaho Economic Development Organization, and other local entities. We are excited to have Dow as a new community partner. They have been wonderful to work with to make this project happen,” he said.

Groundbreaking on the 60,000 square feet project is expected to occur in 2016 with project completion targeted for the latter portion of 2017. Manufacturing of STYROFOAM XPS Insulation is expected to begin in early 2018. Construction of the project will employ approximately 80 workers during peak construction and create 21 full-time manufacturing jobs at the height of operation.

Designing and constructing roof systems (see my previous articles about roof decks, substrate boards and vapor barriers) continues with the thermal insulation layer. The governing building codes will dictate the minimum R-value required and, based on the R-value of the selected insulation, the thickness of required insulation can be determined. This plays into the design of the roof edge, which will be the subject of future articles. For now, let’s focus on insulation.

Photo 1: Polyisocyanurate(ISO) with organic facers

Thermal insulation has multiple purposes, including to:

▪▪ Provide an appropriate surface on which the roof cover can be placed.
▪▪ Assist in providing interior user comfort.
▪▪ Assist in uplift performance of the roof system.
▪▪ Provide support for rooftop activities.
▪▪ Keep the cool air in during the summer and out during the winter, resulting in energy savings.

INSULATION OPTIONS

For the designer, there are numerous insulation material choices, each with its own positive and negative characteristics. Today’s insulation options are:

▪▪ Polyisocyanurate (ISO)

»» Varying densities

»» Organic facers (see photos 1 and 2)

»» Double-coated fiberglass facers (see photo 3)

▪▪ Expanded polystyrene (XPS) (see photo 4)

»» Varying densities

▪▪ Extruded polystyrene (EPS) (see photo 5)

»» Varying densities

▪▪ Mineral wool (see photo 6)

»» Varying densities

▪▪ Perlite
▪▪ High-density wood fiber

With today’s codes, the use of perlite and high-density wood fiber as primary roof insulation is very limited. The R-value per inch and overall cost is prohibitive.

Some attributes of the more commonly used insulation types are:POLYISOCYANURATE

Photo 2: Polyisocyanurate(ISO) with organic facers

▪▪ Predominate roof insulation in the market
▪▪ Organic and double-coated fiberglass facers (mold-resistant)
▪▪ Varying densities available: 18 to 25 psi, nominal and minimum, as well as 80 to 125 psi high-density cover boards
▪▪ Has an allowable dimensional change, per the ASTM standard, that needs to be understood and designed for
▪▪ Can be secured via mechanical fasteners or installed in hot asphalt and/or polyurethane foam adhesive: bead and full-coverage spray foam
▪▪ Has an R-value just under 6.0 per inch but has some downward drifting over time

EXPANDED POLYSTYRENE (EPS)

▪▪ Has good moisture resistance but can accumulate moisture
▪▪ Direct application to steel decks is often a concern with fire resistance
▪▪ Has varying densities: 1.0 to 3.0 pound per cubic foot
▪▪ Very difficult to install in hot asphalt; basically not appropriate
▪▪ Certain products can be secured with mechanical fasteners or lowrise foam adhesive
▪▪ Has stable R-values: 3.1 to 4.3 per inch based upon classification type

EXTRUDED POLYSTYRENE (XPS)

▪▪ Has good moisture resistance and is often used in protected roof membrane systems and plaza deck applications
▪▪ Direct application to steel decks is often a concern with fire resistance
▪▪ Has varying compressive strengths: 20 to 100 psi
▪▪ Not appropriate to be installed in hot asphalt
▪▪ Has stable R-values: 3.9 to 5 per inch based on classification type

MINERAL WOOL

▪▪ Outstanding fire resistance
▪▪ Stable thermal R-value: 4.0 per inch
▪▪ No dimensional change in thickness or width over time
▪▪ Available in differing densities
▪▪ May absorb and release moisture
▪▪ Can be installed in hot asphalt or mechanically attached

Sponsored Messages

@roofingmag on Twitter

January/February 2019

Read our latest issue in digital format.

About Roofing

Roofing is a national publication that unravels, investigates and analyzes how to properly design, install and maintain a roof system. Through the voices of professionals in the field, Roofing’s editorial provides a unique perspective.